The prior art related to the brewing of coffee includes a wide variety of different types of apparatus. One of the problems common to all of this apparatus is the difficulty encountered in producing a satisfactory brew for the entire range of use which includes relatively small numbers of cups and relatively large numbers of cups and also relatively mild brews as well as relatively strong brews.
In order to provide a definition of a desirable brew, the Coffee Brewing Institute has issued a Standard for Ideal Coffee which indicates that an ideal coffee brew consists of a ratio of 10 grams of coffee per 6 ounces of water. The proper technique for preparing mild coffee is to prepare a brew in accordance with the above ratio and then to dilute the brew with hot water to the mild state. This technique is utilized in apparatus which is shown in U.S. Pat. No. 4,108,053 to R. C. Vink and in apparatus which is shown in U.S. Pat. No. 4,056,050 to R. N. Brown.
U.S. Pat. No. 4,108,053 to R. C. Vink shows a device which incorporates a relatively complex valve apparatus to admit heated water to a basket in which coffee has been placed for brewing or, when desired, to permit a portion of the heated water to bypass the coffee basket and then mix with and dilute the coffee brew in order to obtain a weaker brew. The apparatus shown suffers from a number of deficiencies among which is the relatively great complexity of the valve device. Another deficiency is the inability of the apparatus to brew relatively small numbers of cups of coffee, 3 to 5 cups, as well as relatively large numbers of cups of coffee, 12 cups. To overcome this deficiency, the apparatus utilizes a mini basket, FIG. 11, which must be inserted into the main coffee basket. This is a disadvantage because the consumer must store and remember to insert the mini basket when needed and must also carefully measure out the correct amount of coffee using measuring apparatus which is not furnished. In practice, this often results in either too much or too little coffee being used, resulting in either a weak and unsatisfactory brew or too strong a brew and excess use and waste of coffee grounds.
U.S. Pat. No. 4,056,050 to R. N. Brown shows a device which also incorporates a valve mounted above a coffee basket to vary the quantity of heated water which bypasses the coffee basket in order to dilute the coffee brew which has been brewed in the coffee basket. Like U.S. Pat. No. 4,108,053 no provisions are included for accurate measurement of the coffee grounds and like U.S. Pat. No. 4,108,053, the path of the heated water to the coffee grounds is relatively direct with relatively little flow restrictions. This lack of suitable flow restriction often results in too rapid a flow of the heated water through the coffee grounds and insufficient brewing time.
Both the above cited prior art patents teach that in order to brew a specific amount of coffee e.g. number of cups, a fixed amount of ground coffee is used per cup, irrespective of the desired strength. The water bypass structure is employed to vary the strength of the brewed coffee. Thus, except for strong or full strength coffee, satisfactory, efficient extraction of coffee flavor cannot be attained.